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144 results on '"Berger, I. F."'

40. Synthesis, crystal structure and optical properties of Me(OH)(HCOO)2 (Me = Al, Ga).

Author

Krasil'nikov, V. N., Tyutyunnik, A. P., Baklanova, I. V., Enyashin, A. N., Berger, I. F., and Zubkov, V. G.

Subjects
CRYSTAL structure, OPTICAL properties of metals, GALLIUM compounds
Abstract

The formation conditions, crystal structure and luminescence properties of aluminum and gallium hydroxide diformates, Me(OH)(HCOO)2, have been established. Both compounds crystallize in a monoclinic lattice (space group C2, #5 and Z = 8) with parameters: a = 8.8629(2) Å, b = 9.9890(2) Å, c = 10.2411(1) Å, β = 106.223(1)°, and V = 870.56(3) Å3 (Al) and a = 8.8746(1) Å, b = 10.3291(1) Å, c = 10.27870(9) Å, β = 105.7565(6)°, and V = 906.81(2) Å3 (Ga). The emission spectra of Me(OH)(HCOO)2 under UV excitation with wavelength λ = 285 nm exhibit maxima in the range of 440–470 nm. The emission accompanied by light-blue luminescence is greatly enhanced when going from the aluminum to the gallium compound. The origin of intrinsic emission centers responsible for the luminescence properties of Me(OH)(HCOO)2 is suggested and the higher emission of the gallium hydroxide diformate is substantiated by means of density-functional theory calculations. [ABSTRACT FROM AUTHOR]

Published
2018
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42. Synthesis, Crystal Structure and Luminescent Properties of Pyrovanadates A2CaV2O7 (A = Rb, Cs)

Author

Zubkov, V. G., Tyutyunnik, A. P., Tarakina, N. V., Berger, I. F., Surat, L. L., Slobodin, B. V., Svensson, G., Forslund, B., Shulgin, B. V., Pustovarov, V. A., Ishchenko, A. V., and Cherepanov, A. N.

Subjects
RIETVELD REFINEMENT, VANADIUM ALLOYS, ELECTRON-DIFFRACTION DATUM, POWDER METALS, CESIUM, VANADIUM COMPOUNDS, VACUUM ULTRA VIOLETS, CRYSTAL STRUCTURE, ALKALINE METALS, METAL REFINING, UNIT CELL PARAMETERS, BROAD BANDS, LUMINESCENCE CENTERS, RIETVELD METHOD, OXIDES, VANADIUM, ISOSTRUCTURAL, SOLID-STATE REACTIONS, ELECTRON DIFFRACTION, PL EXCITATIONS, TRANSITION METALS, PULSE CATHODE LUMINESCENCE, RUBIDIUM AND CESIUM VANADIUM OXIDE, SPACE GROUPS, PYROVANADATES, LUMI-NESCENT PROPERTIES, LIGHT, EXCITATION BANDS, RUBIDIUM, PHOTOLUMINESCENCE, LIGHT EMISSION, VISIBLE LIGHTS, X-RAY POWDER DIFFRACTION, NEUTRON POWDERS
Abstract

The novel vanadium oxides Rb2CaV2O7 and Cs2CaV2O7 have been prepared by solid-state reaction and their crystal structures determined and refined using X-ray, neutron powder and electron diffraction data. Rb2CaV2O7 and Cs2CaV2O7 are isostructural, crystallizing in space group P21/n with unit cell parameters: a = 13.8780(1), b = 5.96394(5), c = 10.3376(1) Å, β = 104.960(1)° and a = 14.0713(2), b = 6.0934(1), c = 10.5944(1) Å, β = 104.608(1)°, respectively. Their crystal structures can be described as a framework of CaO6 octahedra and V2O7 pyrogroups with alkaline metals found in the tunnels formed. Photoluminescence (PL) and PL excitation spectra of the considered pyrovanadates have been studied in the vacuum ultraviolet (VUV) to visible light (Vis) range as well as their pulse cathode luminescence (PCL) spectra and the kinetic parameters of PCL. In the PL and the PCL spectra of both pyrovanadates recorded at T = 300 K a broad band with maxima at 2.2, 2.4 eV and two shoulders (bands) at 2.0 and 2.58 eV have been observed. At T = 10 K the band at 2.0 eV becomes the main band in the spectra. Two types of luminescence centers for each pyrovanadate, with very similar excitation bands at 3.75, 4.84, 6.2, 7.3 and 9.1 eV, have been found. The nature of the luminescence centers connected with the bands at 2.0, 2.2, 2.4 and 2.58 eV is discussed. © 2008 Elsevier Masson SAS. All rights reserved. This work was supported by the Russian–American program “Fundamental research and higher education” (CRDF REC-005: grant EK-005-X1 fund of the Ural Scientific Educational Center “Perspectivnie materiali”), by the Russian Foundation for Basic Research under Grant No. 07-03-00143, by the Council for Grants of the President of the Russian Federation for Support of Young Scientists (grant no. MK–84.2007.3) and ICDD Grant-in-Aid № 93-09 (2005–2006). Gunnar Svensson wants to thank the Swedish research council for financial support.

Published
2009

45. Cobalt-doped Bi26Mo10O69: Crystal structure and conductivity

Author

Mikhailovskaya, Z. A., Buyanova, E. S., Petrova, S. A., Morozova, M. V., Zhukovskiy, V. M., Zakharov, R. G., Tarakina, N. V., Berger, I. F., Mikhailovskaya, Z. A., Buyanova, E. S., Petrova, S. A., Morozova, M. V., Zhukovskiy, V. M., Zakharov, R. G., Tarakina, N. V., and Berger, I. F.

Abstract

A series of cobalt-doped bismuth molybdates were synthesized and investigated using X-ray powder diffraction, transmission electron microscopy and impedance spectroscopy. The ranges of solid solution were determined. Two new compounds, Bi1-xCox[Bi12O 14]Mo5O34.5 ± δ (x=0.2) and Bi[Bi12O14] Mo5-yCoyO34.5 ± δ (y=0.2), which crystallise in monoclinic unit cells have been examined in detail by diffraction methods. Impedance spectroscopy measurements show that the studied materials are good ionic conductors with conductivity values about 5 × 10-3 S × cm-1 at 973 K and 1.7 × 10-4 S × cm-1 at 623 K, which are similar to conductivity values of yttrium substituted zirconia and (YSZ) gadolinium doped ceria (CGO). © 2013 Elsevier Inc.

Published
2013

46. CRYSTAL STRUCTURE AND VIBRATIONAL SPECTRA OF M[VO(2)(SeO(4))(H(2)O)(2)]center dot H(2)O (M = K, Rb, NH(4))

Author

Tyutyunnik, A. P., Zubkov, V. G., Krasil'nikov, V. N., Berger, I. F., Perelyaeva, L. A., Baklanova, I. V., Skripkin, M. Yu, Svensson, Gunnar, Tyutyunnik, A. P., Zubkov, V. G., Krasil'nikov, V. N., Berger, I. F., Perelyaeva, L. A., Baklanova, I. V., Skripkin, M. Yu, and Svensson, Gunnar

Abstract

By the hydration of MVO(SeO(4))(2) with saturated water vapors at room temperature a series of isostructural complex compounds of vanadium(V) of the composition M[VO(2)(SeO(4))(H(2)O)(2)]center dot H(2)O (K, Rb, NH(4)) are synthesized and their physicochemical properties are studied. Based on the X-ray and neutron diffraction data, it is found that their crystal structure is composed of VO(6) octahedra linked in infinite chains by bridging SeO(4) tetrahedra. Each of the VO(6) octahedra has two short terminal V-O bonds forming a bent dioxovanadium group VO(2)(+). Two water molecules are coordinated by vanadium and one molecule is out of the first coordination sphere in the interchain space. The vibrational spectra of the studied compounds are completely consistent with their structural features., authorCount :8

Published
2011
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47. Structural, vibrational, electronic, and luminescence properties of the cyclotetravanadates A(2)M(VO3)(4) (A=Na,Ag; M=Ca,Sr)

Author

Zubkov, V. G., Surat, L. L., Tyutyunnik, A. P., Berger, I. F., Tarakina, N. V., Slobodin, B. V., Kuznetsov, M. V., Denisova, T. A., Zhuravlev, N. A., Perelyaeva, L. A., Baklanova, I. V., Shein, I. R., Ivanovskii, A. L., Shulgin, B. V., Ishchenko, A. V., Tcherepanov, A. N., Svensson, Gunnar, Forslund, Bertil, Skripkin, M. Yu., Zubkov, V. G., Surat, L. L., Tyutyunnik, A. P., Berger, I. F., Tarakina, N. V., Slobodin, B. V., Kuznetsov, M. V., Denisova, T. A., Zhuravlev, N. A., Perelyaeva, L. A., Baklanova, I. V., Shein, I. R., Ivanovskii, A. L., Shulgin, B. V., Ishchenko, A. V., Tcherepanov, A. N., Svensson, Gunnar, Forslund, Bertil, and Skripkin, M. Yu.

Abstract

The physical properties of the family of cyclotetravanadates A(2)M(VO3)(4), where A=Na,Ag and M=Ca,Sr, have been studied by means of x-ray powder diffraction, neutron diffraction, electron diffraction, infrared, Raman, NMR, photoexcitation and pulse cathode beam excitation, and x-ray photoelectron spectroscopies, and band structure calculations. The differences between the structural, vibrational, luminescence, and electronic properties of the alkali metal-containing [Na2Ca(VO3)(4) and Na2Sr(VO3)(4)] and the d metal-containing cyclotetravanadates [Ag2Ca(VO3)(4) and Ag2Sr(VO3)(4)] are analyzed. Na2Ca(VO3)(4), Ag2Ca(VO3)(4), Na2Sr(VO3)(4), and Ag2Sr(VO3)(4) have tetragonal structures, P4/nbm, with a=10.438 49(6), 10.445 24(5), 10.634 49(4), and 10.625 74(6), and c=4.938 73(5), 4.968 45(5), 4.962 05(4), and 4.979 30(4) angstrom, respectively. The main structural feature of A(2)M(VO3)(4) is the tetracyclic [V4O12] units. The hybridized O 2p-V 3d states of the tetracyclic [V4O12] units have a dominant influence on the electronic structure of these compounds. The compounds are semiconducting with a local density approximation band gap increasing, from 1.85 eV for Ag2Ca(VO3)(4) to 3.02 eV for Na2Ca(VO3)(4). The prospects of these compounds as advanced materials for detectors of photon and corpuscular radiation as well as for color correction of light emission sources such as lamp and light emitting diode sources are discussed., authorCount :19

Published
2008
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